Ink composition, and recorded matter, recording method and recording apparatus using the same

ABSTRACT

An ink composition contains hollow resin particles and an anti-clearing agent preventing the clearing phenomenon of the hollow resin particles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. application Ser. No.12/581,211 filed Oct. 19, 2009 which claims priority to 2008-272269filed Oct. 22, 2008, all of which are incorporated by reference hereinin their entireties.

BACKGROUND

1. Technical Field

The present invention relates to an ink composition, and a recordedmatter, a recording method and a recording apparatus using the inkcomposition.

2. Related Art

U.S. Pat. No. 4,880,465 discloses a white ink composition containinghollow resin particles as a white color material. The hollow resinparticle is defined by an outer shell made of a liquid-permeable resin,having a hollow interior. The hollow interior of the hollow resinparticle of the ink composition filled with a solvent, so that thespecific gravity of the resin particle comes to substantially the sameas that of the ink composition. Consequently, the hollow resin particlescan be stably dispersed in the ink composition. If an image is formed ona recording medium with the ink composition, the solvent filling theinteriors of the hollow resin particles is replaced with air by drying,and the hollow resin particle has a difference in refractive indexbetween the outer shell and the hollow interior. This difference causeslight scattering to produce a hiding power (hence, to produce whitecolor). The outer shell of the hollow resin particle is generally formedof a transparent resin, such as acrylic resin.

Japanese Unexamined Patent Application Publication Nos. 2000-103995,2000-239585 and 2006-56990 disclose techniques for enhancing theejection stability and storage stability of a white ink composition orother color ink compositions. It is however desired that thesetechniques further be improved in terms of the printing properties.

The white ink composition may be used in combination with other colorink compositions (color ink compositions other than white color inkcomposition hereinafter referred to as color ink compositions). From theviewpoint of forming a white hiding layer and of the colorreproducibility, the combinations of these ink compositions may be takenas follows: (i) an image is recorded by forming a white image region anda color image region on a medium; (ii) a white image layer is formedwith a white ink composition, and then a color image layer is formed onthe white image layer with a color ink composition; and (iii) a colorimage layer is formed with an color ink composition, and then a whiteimage layer is formed on the color image layer with a white inkcomposition.

The present inventors have found that long-term storage and ahigh-humidity condition degrade the quality of images formed bycombining a white ink composition containing hollow resin particles anda color ink composition. In the case of (i), the white image regionbecomes clear (transparent) around the boundary between the color imageregion and the white image region. In the cases of (ii) and (iii), thehollow particles present in an image formed by superposing the whiteimage layer and the color image layer one on top of the other becameclear to degrade the color tinge of the recorded image.

SUMMARY

Accordingly, an advantage of some aspects of the invention is that itprovides an ink composition that contains hollow resin particles as acolor material and can form a stable image in combination with othercolor ink compositions. The quality of the image is not degraded withtime and under high-humidity conditions.

The present inventors have found that the clearing phenomenon is causedby the moisturizing agent contained in the color ink composition.

In general, a pigment-based or dye-based ink composition contains amoisturizing agent, such as glycerin or a saccharide, to control theease of ejection and drying, and the moisturizing agent remains inprinted matter to some extent. When a color ink composition and a whiteink composition are combined by a technique, such as above (i) to (iii),the moisturizing agent in the color image region or layer of therecorded image, such as glycerin or saccharide, absorbs water from theair, and leaches the water into the white image region or layer or movesinto the white image region or layer with water held therein, during along-term storage or under a high-humidity condition. The moisturizingagent entering white image region or layer penetrates the hollow resinparticles in the white image region or layer, with water contained.Probably, such hollow resin particles do not scatter light, andtherefore do not produce white color or exhibit hiding power. Thus, thewhite image region becomes clear. This clearing phenomenon was notablyobserved in combined use with a color ink composition containing a colormaterial at a low concentration (containing a moisturizing agent in arelatively high proportion), such as a cyan ink composition or a lightmagenta ink composition.

According to an aspect of the invention, an ink composition is providedwhich contains hollow resin particles and an anti-clearing agentpreventing the clearing phenomenon of the hollow resin particles.

The anti-clearing agent may be a liquid or solid compound having anoctanol/water partition coefficient of more than −0.1 and a vaporpressure of less than 10 Pa at 25° C.

The anti-clearing agent may be at least one compound of hexylene glycoland trimethylolpropane.

The total anti-clearing agent content in the ink composition may be 0.1%to 30% by mass.

The hollow resin particles may have a mean particle size of 0.2 to 1.0μm.

The hollow resin particle content in the ink composition may be 5% to20% by mass.

The ink composition may further contain at least one compound selectedfrom the group consisting of alkanediols and glycol ethers.

The ink composition may further contain an acetylene glycol-basedsurfactant or a polysiloxane-based surfactant.

The ink composition may be used in an ink jet recording technique.

According to another aspect of the invention, a recorded matter isprovided which includes an image formed with the ink composition.

According to still another aspect of the invention, a recording methodis provided which includes forming an image with the ink composition.

According to further aspect of the invention, a recording apparatus isprovided which includes a section recording an image by performing therecording method.

The ink composition according to an embodiment of the invention canproduce a recorded matter including a high-quality image that can bestably stored for a long term even though the image is formed bycombining the ink composition according to an embodiment of theinvention and another ink composition containing a moisturizing agent,for example, by combining a white ink composition of an embodiment ofthe invention and a color ink composition containing a moisturizingagent, because the hollow resin particles in the ink composition of theembodiment do not become clear during a long-term storage and under ahigh-humidity condition.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An ink composition according to an embodiment of the invention will nowbe described in detail.

The invention will be described with reference to an embodiment usinghollow resin particles as a white color material for forming whiteimages. However, the hollow resin particles may have another color otherthan white. For example, the resin forming the hollow resin particlesmay be colored with another color (in this instance, the resin of thehollow resin particles should maintain the optical transparencythereof). As with the white (uncolored) hollow resin particles, thecolored hollow resin particles can also be used for the ink compositionaccording to an embodiment of the invention.

The ink composition may produce a color other than white by combininganother color material with the hollow resin particles.

In the embodiment described below, the ink composition is used as awhite ink composition for forming a white image region, and other inkcompositions containing a moisturizing agent are used as color inkcompositions for forming other color image regions. However, thecombination of the ink compositions is not limited to the embodiment.

An ink composition according to an embodiment of the invention will nowbe described. The ink composition of the embodiment is a white inkcomposition containing hollow resin particles as a white color material.

White Ink Composition 1. Hollow Resin Particles

The hollow resin particles are each defined by an outer shell having ahollow interior. Preferably, the outer shell is made of aliquid-permeable resin. Consequently, if the hollow resin particle ispresent in an aqueous ink composition, the hollow interior is filledwith an aqueous medium. Since the particle filled with an aqueous mediumhas substantially the same specific gravity as the external aqueousmedium, the particle does not sink in the aqueous ink composition and,thus, can maintain the dispersion stability. Thus, the hollow resinparticles can enhance the storage stability and the ejection stabilityof the white ink composition.

After the white ink composition is ejected onto a recording medium, suchas paper, the aqueous medium in the particles is dried to form hollowinteriors. The particles thus contain air. The hollow resin particlesform a resin layer and an air layer having different refractive indices,and thus scatter light effectively to produce white color. The hollowresin particles can be used for other color ink compositions by beingcolored with the resin layers of the particles maintaining the opticaltransparency.

In the present embodiment, a known type of hollow resin particles can beused without particular limitation. For example, the hollow resinparticle disclosed in U.S. Pat. No. 4,880,465 or Japanese UnexaminedPatent Application Publication No. 3,562,754 can be suitably used.

Preferably, the hollow resin particles have a mean particle size (outerdiameter) of 0.2 to 1.0 μm, more preferably 0.4 to 0.8 μm. If the meanparticles size is more than 1.0 μm, the particles may sink to degradethe dispersion stability, or may clog the ink jet recording head todegrade the reliability. In contrast, hollow resin particles having amean particle size of less than 0.2 μm tend to be insufficient inwhiteness. In addition, it is suitable that the hollow resin particlehas an inner diameter of about 0.1 to 0.8 μm.

The mean particle size of the hollow resin particles can be measuredwith a particle size distribution analyzer based on the laserdiffraction/scattering method. A particle size distribution meter usingdynamic light scattering (for example, Microtrack UPA manufactured byNikkiso Co., Ltd.) may be used as the laser diffraction/scatteringparticle size distribution analyzer.

Preferably, the hollow resin particle content in the white inkcomposition is 5% to 20% by mass, more preferably 8% to 15% by mass. Ifthe hollow resin particle content (solid content) is more than 20% bymass, the ink composition may, for example, clog the ink jet recordinghead to degrade the reliability. In contrast, if the hollow resinparticle content is less than 5% by mass, a sufficient whiteness may notbe obtained.

The hollow resin particles can be prepared by a known method withoutparticular limitation. For example, the hollow resin particles can beprepared by so-called emulsion polymerization. In this method, forexample, a vinyl monomer, a surfactant, a polymerization initiator andan aqueous disperse medium are stirred together in a nitrogen atmospherewhile being heated, and thus an emulsion of hollow resin particles isprepared.

Exemplary vinyl monomers include nonionic monoethylene unsaturatedmonomers, such as styrene, vinyl toluene, ethylene, vinyl acetate, vinylchloride, vinylidene chloride, acrylonitrile, (meth)acrylamide, and(meth)acrylic ester. Exemplary (meth)acrylic esters include methylacrylate, methyl methacrylate, ethyl (meth)acrylate, butyl(meth)acrylate, 2-hydroxyethyl methacrylate, 2-ethylhexyl(meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl(meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

The vinyl monomer may be a bifunctional vinyl monomer. Examples of thebifunctional vinyl monomer include divinylbenzene, allyl methacrylate,ethylene glycol dimethacrylate, 1,3-butane-diol dimethacrylate,diethylene glycol dimethacrylate, and trimethylolpropanetrimethacrylate. By polymerizing a foregoing monofunctional vinylmonomer and a bifunctional vinyl monomer to form many cross-links, theresulting hollow resin particles can exhibit heat resistance and solventresistance as well as light scattering characteristics.

The surfactant forms a molecular aggregate such as micelle in water.Examples of such a surfactant include anionic surfactants, nonionicsurfactants, cationic surfactants, and amphoteric surfactants.

The polymerization initiator can be a known compound soluble in water,such as hydrogen peroxide or potassium persulfate.

The aqueous disperse medium can be water that may or may not contain ahydrophilic organic solvent.

2. Anti-Clearing Agent

The ink composition of the present embodiment contains an anti-clearingagent that prevents the clearing phenomenon of the hollow resinparticles.

Preferably, the anti-clearing agent is a liquid or solid compound havingan octanol/water partition coefficient of more than −0.1 and a vaporpressure of less than 10 Pa at 25° C. More preferably, the octanol/waterpartition coefficient is −0.5 or more and the vapor pressure at 25° C.is 3 Pa or less. Although the mechanism of how the clearing phenomenonof the hollow resin particles is prevented is unknown, the following twoare thought of. The anti-clearing agent having the above octanol/waterpartition coefficient exhibits a lower affinity for water than that forthe moisturizing agent in the color image region, and can be presenttogether with the moisturizing agent in a recorded image formed with awhite image region and a color image region. Since the anti-clearingagent has a higher affinity for the moisturizing agent than the affinityfor water in the air, the water cannot penetrate the white image region.If the anti-clearing agent has a vapor pressure of less than 10 Pa at25° C., the anti-clearing agent can remain as a moisturizing agent inthe white image region to prevent water from penetrating from the colorimage region. If the anti-clearing agent is a solid compound, themovement of the anti-clearing agent is minimized in an image.Accordingly, even if the moisturizing agent containing water moves intothe white image region from the color image region, the solidanti-clearing agent traps the moisturizing agent containing water beforethe moisturizing agent penetrates the hollow interiors of the hollowresin particles, and does not move in the image. Thus, the clearingphenomenon of the white image region can be prevented.

Preferably, at least one of hexylene glycol and trimethylolpropane isused as the anti-clearing agent, and more preferably trimethylolpropaneis used. Hexylene glycol and trimethylolpropane as well as glycerin areknown as moisturizing agents used in ink compositions. When hexyleneglycol or trimethylolpropane are used in a white ink compositioncontaining hollow resin particles as a color material, it serves as ananti-clearing agent for the hollow resin particles. Since the clearingphenomenon of the hollow resin particles is thus prevented even during along-term storage or under a high-humidity condition, a recorded matterproduced by recording an image using the white ink composition canmaintain the high-quality image thereof for a long term.

Preferably, the total anti-clearing agent content in the white inkcomposition is 0.1% to 30% by mass, more preferably 0.5% to 20% by mass.

3. Fixing Resin

Preferably, the white ink composition of the present embodiment furthercontains a resin for fixing the hollow resin particles. Examples of sucha resin include acrylic resins (for example, Almatex produced by MitsuiChemicals) and urethane resins (for example, WBR-022U produced by TaiseiFine Chemical).

The fixing resin content in the ink composition is preferably 0.5% to10% by mass, more preferably 0.5% to 3.0% by mass.

4. Penetrating Organic Solvent

Preferably, the white ink composition further contains at least onecompound selected from the group consisting of alkanediols and glycolethers. Alkanediols and glycol ethers can increase the wettability ofthe record surface of the recording medium to enhance the penetration ofthe ink.

Preferred alkanediols are 1,2-alkanediols having a carbon number in therange of 4 to 8, such as 1,2-butanediol, 1,2-pentanediol,1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol. More preferably,1,2-alkanediols having a carbon number of 6 to 8 are used, such as1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol. These alkanediolscan easily penetrate the recording medium.

Exemplary glycol ethers include lower alkyl ethers of polyhydricalcohols, such as ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, ethylene glycol monobutyl ether, diethylene glycolmonomethyl ether, diethylene glycol monoethyl ether, diethylene glycolmonobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycolethyl ether, triethylene glycol monomethyl ether, triethylene glycolmonobutyl ether, and tripropylene glycol monomethyl ether. Triethyleneglycol monobutyl ether can particularly provide a higher record quality.

Preferably, the alkanediol and/or glycol ether content in the white inkcomposition is 1% to 20% by mass, more preferably 1% to 10% by mass.

5. Surfactant

Preferably, the white ink composition of the present embodiment furthercontains an acetylene glycol-based surfactant or a polysiloxane-basedsurfactant. Acetylene glycol-based and polysiloxane-based surfactantscan increase the wettability of the record surface of the recordingmedium to enhance the penetration of the resulting ink.

Examples of the acetylene glycol-based surfactant include2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol,3,5-dimethyl-1-hexyne-3-ol, and 2,4-dimethyl-5-hexyne-3-ol. Acommercially available acetylene glycol-based surfactant may be used,such as OLFINEs E1010, STG and Y (produced by Nissin Chemical Industry);and SURFYNOLs 104, 82, 465, 485, 485 and TG (produced by Air Productsand Chemicals Inc.).

The polysiloxane-based surfactant may be a commercially availableproduct, such as BYK-347 or BYK-348 (produced by BYK).

The white ink composition may contain other surfactants, such as anionicsurfactant, nonionic surfactant, and amphoteric surfactant.

Preferably, the surfactant content in the white ink composition is 0.01%to 5% by mass, more preferably 0.1% to 0.5% by mass.

6. Tertiary Amine

Preferably, the white ink composition further contains a tertiary amine.The tertiary amine can serve as a pH adjuster and can easily control thepH of the white ink composition.

For example, triethanolamine may be used as the tertiary amine.

Preferably, the tertiary amine content in the white ink composition is0.01% to 10% by mass, more preferably 0.1% to 2% by mass.

7. Solvent and Other Additives

The white ink composition generally contains water as the solvent.Preferably, the water is pure water or ultrapure water, such as ionexchanged water, ultrafiltered water, reverse osmotic water, ordistilled water. Particularly preferably, the water is sterilized byirradiating with UV light or adding hydrogen peroxide. Such waterprevents occurrence of molds and bacteria over a long term.

The white ink composition may further contain other additives includinga fixing agent such as water-soluble rosin, an antifungal agent orpreservative such as sodium benzoate, an antioxidant or ultravioletlight adsorbent such as an allophanate, a chelating agent, and an oxygenabsorbent, if necessary. These additives may be used singly or incombination.

The ink composition according to an embodiment of the invention mayfurther contain another color material other than the hollow resinparticles. A general pigment of dye may be used as such a colormaterial.

8. Preparation of Ink Composition

The white ink composition can be prepared in the same manner as knownpigment inks, using a known apparatus, such as ball mill, sand mill,attritor, basket mill or roll mill. For preparation, it is preferablethat coarse particles be removed through a membrane filter or a meshfilter.

The white ink composition can form a white image by being applied onto arecording medium. Examples of the recording medium include paper,cardboard, textile, sheet or film, plastics, glass, and ceramics.

The white ink composition can be used for any application withoutparticular limitation, and can be used for a variety of ink jetrecording methods. Ink jet recording methods include thermal ink jetmethod, piezoelectric ink jet method, continuous ink jet method, rollerapplication, and spray application.

Recorded Matter

A recorded matter according to an embodiment of the invention includesan image recorded using the ink composition described above. The imageof the recorded matter is recorded by combining the ink compositionaccording to an embodiment of the invention and another ink compositioncontaining a moisturizing agent. For example, the white ink compositionaccording to the above embodiment and a general color ink compositioncontaining a moisturizing agent may be combined to produce a recordedmatter. The hollow resin particles in the recorded matter do not becomeclear during a long-term storage and under a high-humidity condition,and the recorded matter can maintain the quality of the image over along term.

Recording Method and Recording Apparatus

The ink composition according to an embodiment can be used in arecording method for recording an image on a recording medium.

Examples of the recording method include, but not limited to, reliefprinting, intaglio printing, planographic printing, mimeographicrecording, electrophotographic recording, thermal ink transfer recordingand ink jet recording. Preferably, ink jet recording is used.

Any known technique can be used for ink jet recording. In particular,superior image recording can be performed by a technique for ejectingdroplets by vibration of a piezoelectric element (recording techniqueusing an ink jet head that forms ink droplets by mechanical deformationof an electrostrictive element) and a technique using thermal energy.

A recording apparatus according to an embodiment of the inventionperforms a recoding method according to an embodiment of the inventionto record an image.

Examples

The invention will be described in detail with reference to Examples.However, it is not limited to the Examples.

1. Preparation of White Ink Composition

According to the compositions shown in Table 1, hollow resin particles,a fixing resin, an organic solvent, an anti-clearing agent, a tertiaryamine, a surfactant and ion exchanged water were mixed by stirring, andthe mixture was filtered through a metal filter of 5 μm in pore size.The filtrate was deaerated with a vacuum pump. Thus, ink compositions ofExamples 1 and 2 and Comparative Examples 1 to 3 were prepared. Thevalues in Table 1 are shown on a percent-by-mass basis, and the valuesof the hollow resin particles are on a solid content basis.

TABLE 1 Example Comparative Example Component 1 2 1 2 3 White hollowresin 10 10 10 10 10 particles SX8782 (D) Solid content: 20.5%Trimethylolpropane 10 — — — — Hexylene glycol — 10 — — — Glycerin — — 10— — Tetraethylene glycol — — — 10 — Polyethylene glycol — — — — 10 Meanparticle size: 400 Urethane resin 5 5 5 5 5 1,2-hexanediol 3 3 3 3 3Triethanolamine 0.5 0.5 0.5 0.5 0.5 BYK-348 0.5 0.5 0.5 0.5 0.5 Ionexchange water Balance Balance Balance Balance Balance Total 100 100 100100 100 Change of color tinge AA A C B C after white and color printingClearing phenomenon in AA A C C C white image region around boundary

Commercially available product SX8782 (D) (produced by JSR) shown inTable 1 was used as the hollow resin particles. SX8782 (D) is of aqueousdispersion type and has a solid content of 20.5%. Its particles have anouter diameter of 1.0 μm and an inner diameter of 0.8 μm.

BYK-348 (produced by BYK) is a polysiloxane-based surfactant.

WBR-022U (produced by Taisei Fine Chemical) was used as the urethaneresin.

For the white ink compositions of Examples 1 and 2, hexylene glycol ortrimethylolpropane was used as the anti-clearing agent. On the otherhand, the white ink compositions of Comparative Examples 1 to 3 usedgeneral moisturizing agents: glycerin, tetra ethylene glycol andpolyethylene glycol (average molecular weight: 400). These moisturizingagents are generally used in ink compositions. Table 2 shows theoctanol/water partition coefficient and the vapor pressure at 25° C. ofthe anti-clearing agents. The octanol/water partition coefficient wasmeasured according to OECD Guideline for the testing of chemicals 107,Partition coefficient (n-octanol/water): Shake flask method, and JIS Z7260-107 (2000), Partition coefficient (1-octanol/water) Shake flaskmethod.

TABLE 2 Octanol/water Vapor pressure partition coefficient (25° C.)Hexylene glycol +0.88  1.7 Pa Trimethylolpropane −0.5 — Glycerin −1.760.01 Pa Tetraethylene glycol −1.36   1 Pa Polyethylene glycol −1.0   10Pa Mean particle size: 400

2. Evaluation

2-1. Change of Color Tinge after White and Color Printing

For printing a white image, the black ink chamber of the cartridge of anink jet printer (PX-G930 manufactured by Seiko Epson) was filled withany one of the white ink compositions shown in Table 1. The inkcartridge was loaded in the printer, and printing tests were performed.

For printing a color image, a commercially available ink jet printer(PX-G5500 manufactured by Seiko Epson) and an ink set (EPSON IC9CL3337including photo black, matte black, gray, light gray, yellow, cyan,light cyan, magenta, and light magenta) were used.

Then, printing was performed on ink jet recording paper (OHP sheet,manufactured by Seiko Epson) at a resolution of 720×720 dpi. The whiteand color images were each formed as a 100% duty-solid pattern.

More specifically, a color image layer was formed on a medium with colorink compositions other than the white ink composition, and subsequently,a white image layer was formed on the color image layer with the whiteink composition.

The change of color tinge of the resulting printed matter was evaluatedunder a high humidity condition, according to the criteria below. Theresults are shown in Table 1.

The L* value was measured with a colorimeter using a black substrate,such as Gretag Macbeth Spectroscan and Spectrolino (manufactured byX-Rite).

The duty mentioned herein is calculated from the following equation:

Duty (%)=number of actually printed dots/(vertical resolution×lateralresolution)×100

(In the equation, the number of actually printed dots refers to thenumber of dots actually printed per unit area, and the verticalresolution and the lateral resolution each refer to a resolution perunit length. A duty of 100% means that a maximum amount of a singlecolor ink is used for an image.)

AA: when an image was allowed to stand under the conditions of atemperature of 27° C. and a humidity of 35% for 24 hours, andsubsequently under the conditions of a temperature of 27° C. and ahumidity of 65% for 24 hours, the reduction in L* value of the colorinks in the white+color image region was less than 2;

A: when an image was allowed to stand under the conditions of atemperature of 27° C. and a humidity of 35% for hours, and subsequentlyunder the conditions of a temperature of 27° C. and a humidity of 65%for 24 hours, the reduction in L* value of the color inks in thewhite+color image region was 2 or more and less than 5;

B: when an image was allowed to stand under the conditions of atemperature of 27° C. and a humidity of 35% for hours, and subsequentlyunder the conditions of a temperature of 27° C. and a humidity of 65%for 24 hours, the reduction in L* value of the color inks in thewhite+color image region was 5 or more and less than 10; and

C: when an image was allowed to stand under the conditions of atemperature of 27° C. and a humidity of 35% for 24 hours, andsubsequently under the conditions of a temperature of 27° C. and ahumidity of 65% for 24 hours, the reduction in L* value of the colorinks in the white+color image region was 10 or more.

2-2. Clearing Phenomenon of White Image Region Around Boundary afterWhite and Color Printing

For printing a white image region, the black ink chamber of thecartridge of an ink jet printer (PX-G930 manufactured by Seiko Epson)was filled with any one of the white ink compositions shown in Table 1.The ink cartridge was loaded in the printer, and printing tests wereperformed. For printing a color image, a commercially available ink jetprinter (PX-G5500 manufactured by Seiko Epson) and an ink set (EPSONIC9CL3337 including photo black, matte black, gray, light gray, yellow,cyan, light cyan, magenta, and light magenta) were used.

Then, printing was performed on ink jet recording paper (OHP sheet,manufactured by Seiko Epson) at a resolution of 720×720 dpi. The whiteand color images were each formed as a 100% duty-solid pattern.

More specifically, a white image region and a color image region wererecorded on a medium so as to come into contact with each other, and theclearing phenomenon with time of the white image region around theboundary between the white image region and the color image region wasevaluated at room temperature, according to the criteria below. Theresults are shown in Table 1.

The white image region and the color image region each had an area of100 mm by 100 mm. For measuring the clearing phenomenon, the L* valuewas measured with a colorimeter using a black substrate, such as GretagMacbeth Spetroscan and Spectrolino (manufactured by X-Rite). It wasdetermined that when the L* value of a portion was reduced by or morefrom the initial value, a clearing phenomenon occurred at the portion.

AA: A clearing phenomenon occurred in a region less than 0.2 mm from theboundary after the image was allowed to stand for a month;

A: A clearing phenomenon occurred in a region from 0.2 mm to less than0.5 mm from the boundary after the image was allowed to stand for amonth;

B: Clearing occurred in a region from 0.5 mm to less than 5 mm from theboundary after the image was allowed to stand for a month; and

C: A clearing phenomenon occurred in a region 5 mm or more from theboundary after the image was allowed to stand for a month.

The recorded matters including images formed by combining a white inkcomposition of Example 1 or 2 and other color ink compositions hardlyexhibited a change of color tinge or a clearing phenomenon in the whiteimage region around the boundary between the color image region and thewhite image region, even during a long-term storage or even under ahigh-humidity condition.

On the other hand, recorded matter including images formed using whiteink compositions of the Comparative Examples notably exhibited clearingphenomena in the white image regions. Probably, the cause of theclearing phenomenon is that the moisturizing agent in the color inkcomposition holds water from the air and, thus, moves the water into thewhite image region, and that the moisturizing agent (glycerin,tetraethylene glycol or polyethylene glycol (average molecular weight:400)) in the white ink composition has an influence on the white imageregion.

What is claimed is:
 1. An ink composition comprising: hollow resinparticles and an anti-clearing agent preventing the hollow resinparticles from becoming clear, wherein the anti-clearing agent is aliquid or solid compound having an octanol/water partition coefficientof more than −0.1 and a vapor pressure of less than 10 Pa at 25° C., andthe hollow resin particles are formed of a resin that has opticaltransparency.
 2. The ink composition according to claim 1, wherein theanti-clearing agent is at least one compound of hexylene glycol andtrimethylolpropane.
 3. The ink composition according to claim 1, whereinthe total content of the anti-clearing agent in the ink composition is0.1% to 30% by mass.
 4. The ink composition according to claim 1,wherein the hollow resin particles have a mean particle size of 0.2 to1.0 μm.
 5. The ink composition according to claim 1, wherein the hollowresin particle content in the ink composition is 5% to 20% by mass. 6.The ink composition according to claim 1, further comprising at leastone compound selected from the group consisting of alkanediols andglycol ethers.
 7. The ink composition according to claim 1, furthercomprising an acetylene glycol-based surfactant or a polysiloxane-basedsurfactant.
 8. The ink composition according to claim 1, wherein the inkcomposition is used in an ink jet recording technique.
 9. A recordedmatter comprising an image formed with the ink composition as set forthin claim
 1. 10. A recording method comprising forming an image with theink composition as set forth in claim
 1. 11. A recording apparatuscomprising a section recording an image by performing the recordingmethod as set forth in claim 10.